Natural, wholesome, inexpensive and available over the counter, St John's wort seemed to be the dream remedy for depression. Taken all over the world in huge quantities, it has become the pill to pop without guilt or fear, the herbal Prozac that dusted away the blues nature's way.

The downside is only now emerging. Although studies show that it is effective for mild to moderate depression and two million British people are taking it, you do have to be careful.

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The chief drawback is that the remedy, derived from the yellow flowering hedgerow plant, interacts with other medicines causing them to metabolise through the body too quickly. This is obviously very significant for people on the contraceptive pill or the blood-thinning medicine warfarin, who are at risk of a stroke.

Warnings issued

At the start of 2000, the Medicines Control Agency issued a warning that patients who are on a long list of medicines should stop taking St John's wort until they have consulted their GP or pharmacist. Medications for asthma, epilepsy, depression, migraine and heart problems are all implicated.

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The authorities in the Irish Republic have gone further by banning the over-the-counter sale of the ancient herbal remedy. It is now available only on prescription.

In the United States, the Food and Drugs Administration (FDA) issued a warning that the herb could interfere with medicines used to treat HIV-infected patients. It also raised the possibility of complications for other patients taking similar medication, including those undergoing heart transplants. The FDA cited research showing that for patients taking St John's wort, the effectiveness of the antiviral medicine indinavir was 'dulled'.

There have also been some reports from America that St John's wort can cause nerve damage or cataracts when combined with bright sunlight. This is believable because herbalists have always known that when St John's wort is used externally, you have to keep out of the sun. Combined with oil, it is used on the skin for paralysis or to treat pain from nerves or shingles.

Researchers have found that hypericin, the active ingredient in St John's wort, does react with sunlight. This is particularly significant for people who suffer from the 'winter blues' or seasonal affective disorder, who might be tempted to combine a course of St John's wort with light-box therapy - sitting for long periods bathed in bright light.

Research findings

Before these recent warnings, medical confidence in St John's wort - known in Latin as Hypericum perforatum - relied heavily on a paper published in the British Medical Journal in August 1996. This research, which took a randomised overview of clinical trials carried out on St John's wort, showed that it was more effective as an antidepressant than placebo (dummy pills). It also appeared to be as good as prescribed antidepressants and to have fewer side effects, but these last two findings were not conclusive.

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It is interesting to note that the researchers, all German scientists, observed that when they began their work in 1994, they could not find a single trial on St John's wort in the English language. Herbal remedies are extensively used in Germany and St John's wort is available on prescription there. In 1994, 66 million prescriptions for the remedy were issued without any reported cases of ill effects.

A more recent trial involving 263 people, also carried out in Germany and published in the British Medical Journal in December 1999, showed that St John's wort was better than placebo and as good as the commonly prescribed antidepressant imipramine. The herbal remedy had fewer side effects and the researchers concluded it showed promise for the long-term treatment of moderate depression.

It is also widely used by Americans who want to treat their own depression, but Dr P. Murali Doraiswamy, a psychiatrist at Duke University, North Carolina, spoke of his reservations at a recent conference, claiming that some of the studies were too small to be reliable and that long-term data was lacking. He also pointed out that the herb had not been compared with the most effective prescription medicines like Prozac and Zoloft (known as Lustral in the UK).

Scientific reviewers called St John's wort promising but unproven, Dr Doraiswamy said, adding that many of his own patients had tried it, but often irregularly and at incorrect doses. Because depression is a serious illness and a major cause of suicide , he said the trend to self-medicate was worrying. Several studies of St John's wort are now in progress in the United States, but early reports suggest these are more negative than positive about the efficacy of St John's wort.

A herbalist's view

Keith Robertson, a qualified herbalist who practises in Glasgow and is Director of Education at the Scottish School of Herbal Medicine, told NetDoctor: 'St John's wort is a gentle herb which I have been prescribing for about 10 years for mild depression. I have not had any problems with it and it seems to work very well.

'It is always better to see herbalists because they usually prescribe four or more remedies at a time. When you buy the tablets over the counter you don't get the whole plant, which can have up to a thousand ingredients. It is the synergy of the different constituents that makes the remedy. I advise patients to have it as a tea or in a tincture - a solution of alcohol. If they cannot consult a herbalist, it is possible to buy the tea or tincture from a herbal shop or by mail order or the Internet.

'Over-the-counter tablets of St John's wort are made up of a standardised extract of hypericin, the active ingredient, without the other substances in the herb. I am concerned that people are taking St John's wort in this way.

'After a few weeks, I usually change the remedy for something else. People shouldn't necessarily take St John's wort in any form all the time. My advice is to give it up when you feel better to see if the depression returns. Unlike prescription antidepressants, herbal medicines work really fast. Keep it for when you need it.

'I am quite convinced that hypericum is safe and that it works to relieve depression if taken at the recommended doses. As with all medication, it shouldn't be mixed with other drugs without consulting a doctor.'

Care is advised

Professor Alasdair Breckenridge, Chairman of the Committee on Safety of Medicines, said doctors should in future ask patients if they are using herbal remedies before prescribing for them. Warnings to appear on the bottles alongside the pretty pictures of the flowering herbs are now commonplace.

Meanwhile, is St John's wort a way forward for the mildly depressed? Probably, but proceed with caution. As Michael McIntyre, chairman of the European Herbal Practitioners Association, summed it up: 'Herbal medicines are potentially very effective and therefore should be prescribed and taken with care. Just because something is natural does not mean it is safe.'

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